The invention relates generally to copolymers of α-methylene-γ-butyrolactone with methyl methacrylate, styrene and, optionally, acrylonitrile, and articles made therefrom.
Polymers made from tulipalin, or α-methylene-γ-butyrolactone (MBL), have been known for more than 50 years (U.S. Pat. No. 2,624,723).
MBL is called tulipalin because it is present in relatively high concentration in white tulips. The homopolymer is a brittle glassy material with a glass transition temperature (Tg) of 195° C. (Macromolecules 12, 546 (1979)). The monomer can be viewed as a cyclic analogue of methyl methacrylate, and its reactivity in free radical polymerizations is comparable or even higher than methyl methacrylate (Akkapeddi, et al., Journal of Polymer Science: Polymer Chemistry Edition, v 20, 2819, (1982) and Polymer, vol 20, 1215, (1979)). The increase in free radical reactivity presumably comes from the ring strain of the molecule.
MBL readily copolymerizes with styrene and (meth)acrylate monomers, and copolymers with (meth)acrylate esters, acrylonitrile and styrene have been reported (Journal of Polymer Science: Polymer Chemistry Edition, v 20, 2819 (1982)). JP 9033736 discloses clear, heat-resistant resins composed of copolymers of MBL with (meth)acrylate monomers. U.S. Pat. No. 5,880,235 discloses MBL copolymers for producing cast glass and thermal dimensionally stable molding materials. U.S. Pat. No. 6,642,346 discloses compositions that include MBL copolymers for automotive clear coats and clear coat finishes. The patent teaches that introduction of an exomethylene lactone or lactam imparts enhanced mar and scratch resistance to the finishes (col. 1, lines 63-65). U.S. Pat. No. 6,723,790 discloses blends of MBL copolymers with other polymers. U.S. Pat. No. 6,841,627 discloses MBL graft copolymers and blends of the copolymers with thermoplastic resins in order to obtain good optical properties and heat and weathering resistance. US 2003/0130414 describes compositions of MBL copolymers filled with alumina trihydrate for decorative sheets and articles The compositions possess thermal resistance, hardness, scratch and mar resistance, antimicrobial properties, lower coefficient of thermal expansion, high refractive index and high transparency. None of the references mention copolymers of MBL with styrene and methyl methacrylate (MMA) that have high Tg, weatherability and solvent resistance.